JP2000257453A - Valve controller for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve startability at low temperature by maintaining a variable valve system to make intake valve operating timing advance when operation stop is detected in a system, which controls the variable valve system so that the intake valve operating timing is delayed when hydraulic pressure decreases. SOLUTION: A variable valve system 32 is composed by making inside of outer periphery of a piston 55 engage with the inner periphery of an outer housing 53 and outer periphery of an inner housing 54 via a helical spline 56. The outer housing 53 is rotated relative to the inner housing 54 according to axial displacement of the piston 55, to change the relative angle of a cam sprocket and an intake cam shaft 51, i.e., the operating timing of an intake valve. In controlling the variable valve system 32 during engine stop with a key switch 20 turned 'OFF', an electromagnetic switching valve 18 is switched to a delay position, and hydraulic fluid from a hydraulic pump is added to the piston 55. Consequently, control for operating timing of the intake valve is set to advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve control system for an engine having a variable valve system.

[0002]

2. Description of the Related Art There has been known a variable valve actuation device in which an operation timing of intake and exhaust valves of an engine is advanced or delayed so as to obtain an optimum intake air filling ratio in accordance with an operation state. I have. The variable valve gear is aimed at achieving high levels of fuel efficiency and output performance, which are generally contradictory requirements. In a hybrid vehicle in which the start and stop of the engine are repeated during traveling, a variable valve train may be used for quick engine start. (Refer to, for example, "Automotive Engineering", Vol. 46, No. 7, June 1997, pp. 39-52, published by Railway Japan Co., Ltd. for known technologies of hybrid vehicles.) Factors that affect the startability of the engine include temperature and lubricating oil. Viscosity, pump loss, etc.
This is a relatively advantageous condition for viscous drag. For this reason, in engines equipped with a variable valve operating system, for example, by delaying the operation timing of the intake valve, the intake filling rate, that is, pump loss at the time of starting cranking is reduced, thereby increasing the cranking speed and realizing a quick start complete explosion. can do. In addition, by reducing the intake air filling rate in this manner, engine vibration at the time of a complete combustion of the engine can be reduced.
On the other hand, in the cold start under extremely low temperature conditions such as in a cold region, the ability of the battery for driving the starter motor is deteriorated, the fuel atomization is worsened, and the friction loss is increased. Is delayed to lower the intake air filling rate, the startability deteriorates.

[0003] On the other hand, in a variable valve operating device in which the valve operation timing is controlled by changing the camshaft phase by hydraulic pressure, noise due to backlash in the mechanism is prevented when the valve operation timing is changed. The return valve biases the variable valve mechanism in the retard direction. This is because, if the valve is biased in the advance direction, a stronger return spring is required to maintain the backlash in a state where the backlash is eliminated against the reaction force from the valve spring at the time of valve operation. This is because, in the control in the angular direction, a disadvantage arises in that a large hydraulic pressure generation source that can counter the control is required. Due to such mechanical requirements, in such a hydraulic variable valve apparatus, when the engine stops and the supply of hydraulic pressure from the hydraulic pump stops, the valve operation timing returns to the most retarded position. However, since it takes some time for the hydraulic pressure to sufficiently rise when the engine is started, when the variable valve operating device is at the most retarded position, this time delay causes insufficient advancement, and as a result, the above-mentioned reason is obtained. This causes a problem that the startability under low-temperature conditions is deteriorated.

The present invention has been made in view of such a problem. In an engine provided with a variable valve operating device configured to urge the intake valve operating timing in a retard direction when the oil pressure drops, The purpose is to improve the startability at low temperatures.

[0005]

According to a first aspect of the present invention, there is provided a variable valve operating device that advances or delays the operation timing of an intake valve in accordance with a hydraulic pressure. In an engine configured to be biased in the angular direction, an operation stop detection device that detects an operation stop condition of the engine and a position where the intake valve operation timing advances the variable valve operating device when the operation stop is detected. And a valve operating time holding device for holding the valve.

According to a second aspect of the present invention, the valve operating timing holding device includes a valve device for shutting off a hydraulic circuit of a variable valve operating device, and a hydraulic supply device for supplying a hydraulic pressure to the hydraulic circuit after the operation is stopped. When the operation stop is detected, the hydraulic supply device is driven to operate the variable valve operating device to the advanced position of the intake valve operation timing, and then the hydraulic circuit of the variable valve operating device is blocked by the valve device.

According to a third aspect of the present invention, there is provided the hydraulic supply device according to the second aspect of the present invention, comprising: a hydraulic pump driven by an engine; and an electric motor for motoring the engine. Is generated.

According to a fourth aspect of the present invention, the hydraulic supply device according to the first aspect of the present invention is constituted by an electric pump.

According to a fifth aspect of the present invention, there is provided the valve operating timing holding device according to the first aspect of the present invention, wherein the holding of the valve operating timing is terminated after the hydraulic pressure supplied to the variable valve operating device increases when the engine is started. Configured.

According to a sixth aspect of the present invention, the valve operating timing holding device according to the first aspect of the present invention is configured to end holding of the valve operating timing when the cooling water temperature is equal to or higher than a predetermined reference value when the engine is started. did.

[0011]

According to the first and second aspects of the present invention, when an engine operation stop condition is detected, the intake valve operation timing is held at the advanced position, and after the engine is stopped, the state is maintained until the next start. Will be kept. That is, when the engine is started next time, the engine can be started with the intake valve operation timing advanced, so that even at a low temperature, the intake charge rate can be increased and good starting performance can be ensured.

As a valve operating timing holding device for holding the intake valve operating timing of the variable valve operating device at the advanced position, the hydraulic circuit of the variable valve operating device after the engine is stopped as described in the second aspect of the present invention. It is possible to adopt a configuration that shuts off the power, so that the object can be achieved with a simple configuration using the hydraulic circuit.

[0013] As a hydraulic supply device for supplying a hydraulic pressure for moving the intake valve operation timing to an advanced position when the engine is stopped, an electric motor for motoring the engine and an electric motor for motoring the engine are provided. It can be configured with an engine-driven hydraulic pump, and this can be easily realized in a hybrid vehicle or the like having an electric motor for motoring. In the case where such an electric motor for motoring is not provided, hydraulic pressure can be supplied by an electric pump as described in the invention of claim 4.

The operation timing of the intake valve by the variable valve operating system can be freely controlled after starting by the hydraulic pressure which rises after the engine is started. Thus, the holding at the advanced position can be terminated. The increase in the oil pressure at this time can be determined by estimating the elapsed time after the start, in addition to detecting the actual oil pressure by providing a hydraulic switch.

According to the present invention, when the cooling water temperature at the time of starting is equal to or higher than a certain reference value, the holding of the valve operating timing is terminated, and the engine is started with the intake valve operating timing delayed. As a result, under relatively high temperature atmosphere conditions with good startability, the start-up vibration can be reduced by retarding the intake valve operation timing.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 first? FIG. 2 shows a configuration example of a hybrid vehicle to which the present invention can be applied. This is a parallel hybrid vehicle that travels using the power of one or both of an engine and an electric motor according to traveling conditions.

In FIG. 1, a thick solid line indicates a transmission path of mechanical force, and a thick broken line indicates a power line. Further, a thin solid line indicates a control line, and a double line indicates a hydraulic system. The power train of this vehicle includes a motor 1 (electric motor of the present invention), an engine 2, a clutch 3, a motor 4, a continuously variable transmission 5, a reduction gear 6, a differential gear 7, and driving wheels 8. Output shaft of motor 1, output shaft of engine 2, and clutch 3
Are connected to each other. The motor 1 and the engine 2 are connected to each other via a reduction gear (not shown) having a predetermined rotation ratio. Also, clutch 3
, The output shaft of the motor 4 and the input shaft of the continuously variable transmission 5 are connected to each other.

When the clutch 3 is engaged, the engine 2 and the motor 4
Is the propulsion source of the vehicle, and when the clutch 3 is released, only the motor 4 is the propulsion source of the vehicle. The driving force of the engine 2 or the motor 4 is controlled by a continuously variable transmission 5, a reduction gear 6, and a differential gear 7.
Is transmitted to the drive wheels 8 via the Pressure oil is supplied from the hydraulic device 9 to the continuously variable transmission 5 to clamp and lubricate the belt. An oil pump (not shown) of the hydraulic device 9 is driven by a motor 10.

The motor 1 is mainly used for engine starting and power generation, and the motor 4 is mainly used for propulsion (powering) and braking of the vehicle. The motor 10 is for driving the oil pump of the hydraulic device 9. Further, when the clutch 3 is engaged, the motor 1 can be used for propulsion and braking of the vehicle, and the motor 4 can be used for starting the engine and generating power. The clutch 3 is a powder clutch, and can adjust the transmission torque. The continuously variable transmission 5 is a continuously variable transmission of a belt type, a toroidal type, or the like, and can continuously adjust the speed ratio.

The motors 1, 4, and 10 are driven by inverters 11, 12, and 13, respectively. When a DC electric motor is used for the motors 1, 4, and 10, a DC / DC converter is used instead of the inverter. The inverters 11 to 13 are connected to a main battery 15 via a common DC link 14,
Converts the DC charging power to AC power and
0, and converts the AC power generated by the motors 1 and 4 into DC power to charge the main battery 15. Since the inverters 11 to 13 are connected to each other via the DC link 14, the power generated by the motor during the regenerative operation can be directly supplied to the motor during the power running operation without passing through the main battery 15. it can. Various batteries such as a lithium ion battery, a nickel hydride battery, and a lead battery, and an electric double layer capacitor, a so-called power capacitor, are applied to the main battery 15.

Reference numeral 16 denotes a controller having the functions of the control device of the present invention. The controller 16 includes a microcomputer and its peripheral parts, various actuators, etc., and transmits torque of the clutch 3, rotation speeds of the motors 1, 4, and 10, and output torque. , The speed ratio of the continuously variable transmission 5, the fuel injection amount / injection timing of the engine 2, the ignition timing, and the like.

As shown in FIG. 2, the controller 16 includes a key switch 20, a select lever switch 21,
Accelerator pedal sensor 22, brake switch 23, vehicle speed sensor 24, battery temperature sensor 25, battery SO
A C detection device 26, an engine speed sensor 27, a throttle opening sensor 28, and a water temperature sensor 29 are connected. The key switch 20 corresponds to the operation stop detection device of the present invention, and closes when the vehicle key is set to the 0N position or the START position (hereinafter, the switch is turned on or 0N, and the open circuit is turned off or OFF). ). The select lever switch 21 is operated according to a set position of a select lever (not shown) for switching to any of the parking P, neutral N, reverse R, and drive D ranges.
One of the switches P, N, R, and D is turned on.

The accelerator pedal sensor 22 detects the amount of depression of the accelerator pedal, and the brake switch 23 detects the state of depression of the brake pedal. Vehicle speed sensor 24
Detects the running speed of the vehicle, and the battery temperature sensor 25 detects the temperature of the main battery 15. Battery SOC
The detecting device 26 detects an SOC (State Of Charge) which is a representative value of the actual capacity of the main battery 15. The engine speed sensor 27 detects the speed of the engine 2, and the throttle opening sensor 28 detects the throttle valve opening of the engine 2. Further, the water temperature sensor 29 detects a cooling water temperature of the engine 2.

The controller 16 is also connected to a fuel injection device 30, an ignition device 31, and a variable valve device 32 of the engine 2. The controller 16 controls the fuel injection device 3
0 to control the supply and stop of the fuel to the engine 2 and the fuel injection amount / injection timing.
To control the ignition timing of the engine 2. Further, the controller 16 controls the variable valve operating device 32 to adjust the operation state of the intake and exhaust valves of the engine 2. The controller 16 is supplied with power from a low-voltage auxiliary battery 33.

Next, a specific configuration example of the variable valve operating device 32 applied to the engine 2 will be described with reference to FIGS. FIG. 3 shows the details of the mechanism of the variable valve operating device, and FIG. 4 shows a control system centering on the hydraulic circuit.

The variable valve train 32 includes an intake camshaft 51
The intake valve actuation timing is advanced or retarded by variably transmitting the rotation phase of a cam sprocket (not shown) to the intake camshaft 51. Reference numeral 53 denotes an outer housing to which the cam sprocket is attached, and reference numeral 54 denotes an inner housing coupled to the intake camshaft 51. The inner housing 53 is axially displaced into an annular space between the inner periphery of the outer housing 53 and the outer periphery of the inner housing 54. A possible annular piston 55 is accommodated.

The inner circumference and outer circumference of the piston 55, the inner circumference of the outer housing 53, and the outer circumference of the inner housing 54 are slidably engaged in the axial direction via helical splines 56, respectively. In response, the outer housing 53 and the inner housing 54 rotate relative to each other to change the relative angle between a cam sprocket (not shown) and the intake camshaft 51, thereby changing the intake valve operation timing.

The position of the piston 55 is controlled by hydraulic pressure. For this reason, an advanced oil chamber 57 is provided at a position where the piston 55 opposes the end of the outer housing 53, and a retarded oil chamber 57 is provided at the intake camshaft 51 side. Side oil chambers 58 are respectively defined. A coil-shaped return spring 52 is housed in the retard-side oil chamber 58, and the tension of the return spring 52 urges the piston 55 in the retard direction.

The oil chambers 57 and 58 are connected to an engine-driven hydraulic pump 17 (see FIG. 4) through a journal section supporting the intake camshaft 51 and an oil passage 59 or 60 formed inside the intake camshaft 51. It is connected. Oil passage 5
An electromagnetic switching valve 18 is interposed in the middle of 9 and 60,
By controlling the position of the electromagnetic switching valve 18 by the controller 16, the position of the piston 55 is controlled to an arbitrary position on the advance side or the retard side.

The electromagnetic switching valve 18 corresponds to the valve operating timing holding device of the present invention, and as shown in FIG.
In the position a shown in the figure, the advance-side oil chamber 57 and the hydraulic pump 17 are connected, and the retard-side oil chamber 58 is connected to the drain. It moves to the advance side against the return spring 52 to advance the intake valve operation timing. At the b position, the retarding oil chamber 58 and the hydraulic pump 17 are connected to each other and the advancing oil chamber 57 is connected to the drain. Delay the operation timing. The c position is a position for the position holding operation, and the oil passages 59, 6 to the oil chambers 57, 58 are provided.
In order to shut off 0, the piston 55 is locked. When the engine 2 is stopped and the oil pressure is reduced at the a or b position, the piston 55 is urged in the retard direction by the tension of the return spring 52.

During operation of the engine, the controller 16 controls the electromagnetic switching valve 18 while detecting the operating state such as the engine speed and the required load so that a predetermined intake valve operation timing is obtained according to the operating state. In this case, the control of the intake valve operation timing is performed based on the cooling water temperature obtained from the water temperature sensor 29 and the state of the key switch 20 indicating the engine stop condition. When it is necessary to supply oil pressure to the variable valve operating device 32 after stopping the engine, the controller 16 motors the engine 2 by the motor 1, thereby causing the hydraulic pump 17 to generate oil pressure. That is, the motor 1 and the hydraulic pump 17 correspond to a hydraulic supply device of the present invention.

Next, an embodiment of the intake valve operation timing control by the controller 16 will be described with reference to FIGS. FIG. 5 and FIG.
3 is a flowchart showing an outline of the control of the hybrid vehicle, and the processes represented by these flowcharts are periodically executed by interrupt processing or the like as a part of the overall control of the hybrid vehicle by the controller 16.

FIG. 5 shows control when the engine is stopped. In this control, the state of the key switch 20 is first detected, and the state of the key switch 20 is turned on at the previous detection and turned off at the current detection. If the key switch 20 becomes ON or OFF, the engine stop condition is determined to be not an engine stop condition. The control for advancing the intake valve operation timing is not executed (step 501). In a hybrid vehicle, the engine may be stopped even when the automatic transmission is operated in the parking range. Therefore, the selection operation of the transmission may be detected from the select lever switch 21 (see FIG. 2). Good.

When it is determined that the engine is stopped, the electromagnetic switching valve 18 is controlled to the a position. At this time, since the engine 2 has already been stopped, the motor 1 is used for motoring, and the hydraulic pump 17 is turned off. It operates to generate hydraulic pressure (steps 502 to 503). In addition,
The hydraulic pump 17 as a hydraulic source is normally driven by the crankshaft of the engine, but the hydraulic pressure may be generated by an external electric pump or the like in order to supply a higher hydraulic pressure to the engine. Further, in the present embodiment, control is performed to advance the intake valve operation timing after the engine is stopped.However, control is performed to advance the intake valve operation timing before the engine is stopped. The engine may be stopped. The hydraulic pressure supply at this time is continued until it is determined that the variable valve operating device 32 has reached the predetermined advance position based on, for example, the elapsed time from the start of the hydraulic pressure supply (step 504).

Next, when the variable valve operating device 32 reaches a predetermined advanced angle position, the friction of the variable valve operating device 32 is greater than the tension of the return spring 52, so that when the engine is stopped, the variable valve operating device 32 is stopped. Piston 55
Does not move, and the variable valve operating device 32 is fixed at the advanced position.
Thereafter, in order to ensure quick response of the variable valve operating device 32 at the time of the next engine start, the electromagnetic switching valve 18 is switched to the c position, which is the lock position, and the oil chamber 57, 58 is in a hydraulically locked state (step 505). After maintaining the intake valve operation timing at the advanced position in this way, the motor 1 is stopped to terminate the supply of the hydraulic pressure, and the power is turned off to complete the control when the engine is stopped (steps 506 to 507).

Based on the above control, the variable valve operating device 32 keeps the intake valve operation timing at the advanced position even after the engine is stopped. Therefore, at the next start, even if the engine oil pressure does not rise sufficiently, the operation of the intake valve is started. The engine can be started with the timing advanced, so that even at a low temperature, a necessary compression pressure can be secured and good startability can be exhibited.

Next, an embodiment of control at the time of starting the engine will be described with reference to FIG. In this start-time control, first, it is determined from the fact that the engine key switch 20 has been set to the START position, or in the case of a hybrid vehicle, the select lever of the transmission has been operated from parking to the travel range, and so on. In some cases, the following start-time control is performed, and when the start condition is not determined, the control is not performed (step 601).

If it is determined that the engine is in the starting condition, the engine cooling water temperature Tw is detected based on a signal from the water temperature sensor 29, and is compared with a predetermined reference water temperature To (step 602). The reference water temperature To is set near the lower limit temperature at which good startability can be obtained even when the intake valve operation timing is in the retarded state. In other words, when the cooling water temperature Tw is equal to or higher than To, the engine can be started without advance of the intake valve operation timing. Therefore, the engine is stopped at the c position (advance angle holding state) by the engine stop control shown in FIG. The electromagnetic switching valve 18 is switched to the position b to delay the operation timing of the intake valve, and then the motor 1 is used to start cranking until the engine is completely exploded. Control is performed to switch the electromagnetic switching valve 18 to the a position to advance the intake valve operating position (steps 609 to 611, 607). This makes it possible to reduce the compression pressure and reduce the vibration at the time of starting the engine under the condition that the startability is good at a relatively high temperature.

On the other hand, when the cooling water temperature Tw is lower than the reference value To, the electromagnetic switching valve 18 is maintained at the position c, that is, while the intake valve operation timing is advanced,
Start cranking is performed until the engine has completely started (steps 603 to 606). However, if the cranking continues for a certain period of time, the engine oil pressure is increased by the hydraulic pump 17 during that time.
At this time, the electromagnetic switching valve 18 is switched to the a position (steps 605 and 60).
8). On the other hand, if the engine is completely exploded before the engine oil pressure sufficiently rises, the electromagnetic switching valve 18 is switched to the a position as necessary after the complete explosion of the engine (step 607).

According to this start-time control, the engine can be started by holding the intake valve operation timing in the advanced state without waiting for the engine oil pressure to rise. And good startability can be ensured. On the other hand, under relatively high temperature conditions with good engine startability, the intake valve operation timing is retarded and started as described above, so that the effect of reducing vibration at the time of engine start can also be enjoyed.

[Brief description of the drawings]

FIG.

FIG. 2 is a schematic configuration diagram illustrating a configuration example of a hybrid vehicle including a variable valve apparatus to which the present invention can be applied.

FIG. 3 is a longitudinal sectional view of an embodiment of the variable valve device.

FIG. 4 is a schematic diagram of a control system including a hydraulic circuit and the like of the variable valve operating device.

FIG.

FIG. 6 is a flowchart of an embodiment relating to control contents of the variable valve operating device according to the present invention.

[Description of Signs] 1 Electric motor 2 Engine 3 Clutch 4 Electric motor 5 Continuously variable transmission 9 Hydraulic device 10 Hydraulic pressure generating motor 15 Battery 16 Controller 17 Hydraulic pump 18 Electromagnetic switching valve (valve operation timing holding device) 20 Key switch 21 Select lever switch 22 Accelerator pedal sensor 23 Brake switch 24 Vehicle speed sensor 25 Battery temperature sensor 26 Battery SOC detection device 27 Engine speed sensor 28 Throttle opening sensor 29 Water temperature sensor 32 Variable valve gear 51 Intake camshaft 53 Outer housing 54 Inner housing 55 Piston 57 Advance oil chamber 58 Delay oil chamber

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 2, 1999 (1999.4.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration example of a hybrid vehicle including a variable valve apparatus to which the present invention can be applied.

FIG. 2 is a schematic configuration diagram illustrating a configuration example of a hybrid vehicle including a variable valve apparatus to which the present invention can be applied.

FIG. 3 is a longitudinal sectional view of an embodiment of the variable valve device.

FIG. 4 is a schematic diagram of a control system including a hydraulic circuit and the like of the variable valve operating device.

FIG. 5 is a flowchart of an embodiment relating to control contents of the variable valve operating device according to the present invention.

FIG. 6 is a flowchart of an embodiment relating to control contents of the variable valve operating device according to the present invention.

[Description of Signs] 1 Electric motor 2 Engine 3 Clutch 4 Electric motor 5 Continuously variable transmission 9 Hydraulic device 10 Hydraulic pressure generating motor 15 Battery 16 Controller 17 Hydraulic pump 18 Electromagnetic switching valve (valve operation timing holding device) 20 Key switch 21 Select lever switch 22 Accelerator pedal sensor 23 Brake switch 24 Vehicle speed sensor 25 Battery temperature sensor 26 Battery SOC detection device 27 Engine speed sensor 28 Throttle opening sensor 29 Water temperature sensor 32 Variable valve gear 51 Intake camshaft 53 Outer housing 54 Inner housing 55 Piston 57 Advance oil chamber 58 Delay oil chamber

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 3G092 AA11 AC02 BA09 BB01 BB06 DA01 DA09 DF04 DF08 DG02 DG05 DG08 DG09 EA03 EA08 EA12 EA13 EA28 FA31 FA50 GA01 GA10 HA06Z HA13X HE01Z HE08Z HF02Z HF08Z12 HF08Z12 HF08Z12

Claims (6)

[Claims] 1. An intake valve operating timing is advanced during a hydraulic operation,
An engine provided with a variable valve device configured to delay the operation timing of the intake valve by a return spring when the hydraulic pressure is released, an operation stop detection device detecting an engine operation stop condition, and A valve actuation control device for an engine, comprising: a valve actuation timing holding device for holding a valve device at a position where an intake valve actuation timing is advanced. 2. A valve operating timing holding device comprising: a valve device for blocking a hydraulic circuit of a variable valve operating device; and a hydraulic supply device for supplying a hydraulic pressure to the hydraulic circuit after an operation is stopped. 2. The engine operating system according to claim 1, wherein the supply device is driven to operate the variable valve operating device to the advanced position of the intake valve operation timing, and then the hydraulic circuit of the variable valve operating device is shielded by the valve device. Valve control device. 3. The hydraulic supply device according to claim 2, wherein the hydraulic supply device includes a hydraulic pump driven by the engine, and an electric motor for motoring the engine, and the hydraulic pump is configured to generate a hydraulic pressure by the motoring. Engine valve control device. 4. The valve operating control device for an engine according to claim 2, wherein the hydraulic supply device is constituted by an electric pump. 5. A valve operating system for an engine according to claim 1, wherein the valve operating timing holding device is configured to stop holding the valve operating timing after the hydraulic pressure supplied to the variable valve operating device increases when the engine is started. Control device. 6. The valve actuation control of an engine according to claim 1, wherein the valve actuation timing holding device terminates the holding of the valve actuation timing when the cooling water temperature is equal to or higher than a predetermined reference value when the engine is started. apparatus.